Immunology

Basophil – Definition, Structure, Functions

Basophils are an immunological cell type that release enzyme-containing granules during allergic responses and asthma crises. Basophil is a type of white...

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This article writter by MN Editors on November 05, 2022

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Basophil - Definition, Structure, Functions
Basophil - Definition, Structure, Functions

Basophils are an immunological cell type that release enzyme-containing granules during allergic responses and asthma crises. Basophil is a type of white blood cell that, together with neutrophils and eosinophils, belongs to the granulocytes category.

They contain several chemicals, including histamine and heparin. As part of the body’s immune response, basophils degranulate (split open) to release these chemicals after an allergic reaction. These cells serve a variety of activities to safeguard our bodies, and there are a number of diagnostic tests available to determine the extent of any damage or disease we may be experiencing.

What are Basophils?

  • Granulocytes and Agranulocytes are the two types of white blood cells, commonly known as leukocytes, based on the presence or lack of granules.
  • Granulocytes include neutrophils, eosinophils, and basophils, which contain granules.
  • Granulocytes collaborate to treat diseases or allergies in the human body. Each type of granulocyte contains a distinct combination of chemicals and enzymes within its granules.
  • Basophils are the smallest granulocytes, with a diameter of 10 to 14 m.
  • These polymorphonuclear cells contain a bilobed nucleus and highly metachromatic cytoplasmic granules.
  • They only live for one to two days.
  • These are the only histamine-containing leukocytes that circulate in the body.
3D rendering of a basophil
3D rendering of a basophil | Image credit: Blausen Medical, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Structure of Basophils

  • When basophils are labelled, their enormous cytoplasmic granules hide the cell nucleus under the microscope. However, when the nucleus is unstained, its two lobes are typically visible.
  • Another granulocyte with a similar look and function is the mast cell.
  • Both cell types store the chemical histamine, which is produced by activated cells.
  • Mast cells, however, originate from separate branches of hematopoiesis and are typically found in connective tissue rather than the bloodstream.
  • When necessary, basophils, like other circulating granulocytes, can be recruited from the blood into a tissue.
Basophils
Basophils | Image Credit: Guy Waterval, Apache License 2.0 http://www.apache.org/licenses/LICENSE-2.0, via Wikimedia Commons

Development of Basophils

  • In the bone marrow, these cells grow alongside neutrophils and eosinophils. It is believed that a basophil has a maximum lifespan of 70 hours.
  • Basophils originate from a shared progenitor cell with eosinophils and neutrophils.
  • It is not understood how basophils differentiate from other cell types, however the emergence of IL-3 appears to correspond with this process.
  • It has been demonstrated that IL-3 promotes the development of bone marrow precursor cells. In contrast to mast cells, human basophils circulate and may be drawn to locations of an inflammatory response, but will not be identified in normal tissue.
  • Basophils originate from hemopoietic stem cells influenced by a myeloid progenitor.
  • Development will proceed in the bone marrow or spleen as a pre-basophil/mast cell progenitor.
  • Basophils are discharged into the bloodstream, where they await stimulation by an allergen or other stimulus.
  • They can also be activated by immunoglobulin, cytokines, or other growth factors, as well as bacteria or bacterial subparticles, particularly in the case of parasites, viruses, or allergies.

Microscopic (histologic) description

  • Basophilic granules are metachromatic (reddish purple) and water-soluble with Toluidine blue and Alcian blue.
  • Basophilic myeloblast: difficult to differentiate from other granulocyte blasts; big, spherical cells with basophilic cytoplasm and no granules; N/C ratio of 80%. scattered chromatin including nucleolus
  • Basophilic promyelocyte: developmental intermediate between basophilic myeloblast and myelocyte; big, circular cell with undifferentiated cytoplasmic granules; Slight chromatin clustering, presence of nucleolus
  • Basophilic myelocyte: Basophilic myelocytes are often larger than neutrophilic granules. N/C ratio is fifty percent; moderately compacted chromatin; no distinct nucleolus
  • Basophilic metamyelocyte: oval cell with abundant pale cytoplasm, big and rather uniform specific granules; N/C ratio of 40%; tiny, indented nucleus with condensed chromatin; absence of nucleolus.
  • Basophil: smaller than normal white blood cells (10 – 15 microns); cytoplasm is pale blue but frequently hidden by purple blue granules (carrying heparin and histamine); N/C is 20%; nucleus is frequently unsegmented or bilobed, chromatin is coarse.

Action of Basophils

  • Basophils contribute to the activation of inflammatory reactions.
  • Inflammation is the body’s natural response to anything that could be harmful.
  • It is the body’s way of instructing the immune system to mend and restore damaged tissues while defending against foreign invaders.
  • Histamine and heparin are among the chemicals present in basophil granules.
  • Function of Histamine: It is a vasodilator, meaning it widens blood vessels. This draws additional immune cells to the damaged or infected area.
  • Function of Heparin: It has anti-coagulant properties (blood thinner). The body produces it to prevent blood clots from forming at the site of an injury or infection.
  • Additionally, basophils indirectly target foreign agents by binding to B-cell lymphocytes.
  • As a result of the binding, B-cells release antibodies known as immunoglobulin E (IgE) into the bloodstream.
  • IgE possesses potent anti-parasite and anti-venom properties.

Basophils Role in Allergies

  • An allergy occurs when the immune system reacts abnormally to an otherwise harmless chemical or event.
  • The release of histamine by basophils is one of the primary causes of allergy symptoms.
  • When the body is exposed to allergens, basophils and similar cells called mast cells burst open (allergy-causing chemical).
  • Histamine causes blood arteries to widen, allowing surrounding tissues to receive fluid.
  • As these tissues expand and become inflamed, they can cause skin inflammation, redness, and itching in the form of rashes and hives.

Levels of Basophils

  • The concentration of white blood cells, of which basophils comprise between 0.5 and 1 percent, is determined by a test called a white blood cell (WBC) count.
  • Absolute basophil count (ABC) is a test that measures the precise amount of basophils in millilitres (mm3).
  • The usual range for basophils is 0.5% to 1% of the total white blood cell count. This corresponds to zero to 300 basophils per microliter of blood in healthy humans.
  • If your basophil count exceeds this threshold, you may be suffering from allergic responses, chickenpox, collagen vascular disease, hyperthyroidism, or bone marrow illness.
  • Cancer, acute infection, and thyrotoxicosis are denoted by a decrease in basophils.
  • Blood testing may reveal elevated or depleted levels of basophils in response to particular illnesses or treatments.
  • Basophilia is characterised by an abnormally high basophil count, and basopenia is characterised by an abnormally low basophil count.

Function of Basophils

  • Basophils are one of five types of white blood cells that protect the body against infection and respond to foreign invaders such as parasites, fungi, and cancer cells.
  • They are part of the innate immune system, which is the immunity present at birth.
  • Basophils are responsible for regulating the human body’s reaction to allergens.
  • When we come into contact with allergens, we experience sneezing, coughing, and runny nose.
  • Early-stage cancer cells can be identified and eliminated.
  • Basophils also release histamine from their granules during an allergic reaction or asthma attack, which plays a key role.
  • In addition, they protect our bodies from microbiological diseases, viruses, parasites, etc.
  • They are essentially the first line of defence against any foreign agent that enters the body.

References

  • Sticco KL, Pandya NK, Lynch DT. Basophilia. [Updated 2022 Oct 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535365/
  • https://www.medicalnewstoday.com/articles/324188
  • https://www.verywellhealth.com/what-are-basophils-797206
  • https://www.sciencedirect.com/topics/engineering/basophil
  • https://www.pathologyoutlines.com/topic/bonemarrowbasophils.html
  • https://www.oatext.com/the-basophil.php
  • https://www.akadeum.com/types-of-cell-separation/granulocyte-isolation-from-whole-blood-types-of-granulocytes-and-granulocytes-function/what-are-basophils-leukocyte-isolation-and-leukopak-processing-with-bacs/
  • https://www.thermofisher.com/in/en/home/life-science/cell-analysis/cell-analysis-learning-center/immunology-at-work/granulocyte-cell-overview/basophil-overview.html
  • https://www.healthline.com/health/basophils#what-happens-if-yourlevel-is-high
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Microbiology Notes is an educational niche blog related to microbiology (bacteriology, virology, parasitology, mycology, immunology, molecular biology, biochemistry, etc.) and different branches of biology.

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